score = input("请输入一个0-100的整数：")
score = int(score)

# 如果成绩大于等于90分，grade赋值为'A'
if score >= 90:
    grade = 'A'
    print(grade)
# 否则如果成绩大于等于80分，grade赋值为'B'
elif score >= 80:
    grade = 'B'
    print(grade)
# 否则如果成绩大于等于70分，grade赋值为'C'
elif score >= 70:
    grade = 'C'
    print(grade)
# 否则如果成绩大于等于60分，grade赋值为'D'
else:
    if score >= 60:
        grade = 'D'
        print(grade)

    # 否则，grade为'E'
    else:
        grade = 'E'
        print(grade)

